Known devices for applying drops of medicament into an eye typically comprise a flexible vial containing the medicament and a nozzle attached over an opening of the vial for releasing drops of medicament into the eye. In some known devices the nozzle comprises a relatively long and narrow tip, referred to by those skilled in the art as an ocumeter. The ocumeter is generally provided to increase the user's control over the size of each drop and the number of drops released from the vial. Drops are applied to the eye by pointing the nozzle toward the open eye and squeezing the vial to release one or more drops of medicament into the eye.
Other known devices store the medicament in a vial and employ a separate eyedropper to release the drops of medicament into the eye. Eyedroppers typically comprise a small tube having a nozzle formed on one end and a suction bulb attached to the other end. The medicament is drawn into the tube by squeezing the suction bulb and inserting the tube into the vial. The suction bulb is then released to draw the medicament into the tube. Drops of medicament are applied to the eye by pointing the tube toward the eye and squeezing the suction bulb to release the drops of medicament into the eye.
People frequently encounter difficulty in applying eyedrops with these known devices For example, many people have poor vision and/or their hands may shake and, thus, they have difficulty handling small eyedroppers. This can be especially dangerous if the user accidentally touches the cornea of the eye with the tip of the eyedropper. The cornea is an extremely sensitive area and can be easily damaged. Moreover, elderly people frequently have arthritis or other ailments disabling their fingers so that it can be extremely painful, and in some cases impossible, for these people to squeeze a device to release the eyedrops. This problem is especially critical with ocumeter devices because the impedance to fluid flow created by the ocumeter requires a greater squeezing force on the vial than with other devices. As a result, the users usually cannot accurately control the way they squeeze the vial or dropper and force too many drops through the nozzle. Likewise, because the users have difficulty squeezing the vial or dropper, they have trouble aiming the eyedrops into their eyes. Accordingly, in many instances, the degree of ophthalmologic patient compliance with such known devices is unacceptably low.
The maximum volume of liquid medicament that should be introduced into an eye at one time is about 25 microliters. Any amount greater usually spills over the eyelid and onto the person's cheek. Accordingly, another problem associated particularly with devices employing an eyedropper or squeeze vial is that both the volume of the drops, and the number of drops released from such devices cannot be accurately controlled. If the vial or eyedropper is squeezed with too much force, the volume of each drop may well exceed 25 microliters and, frequently, more than one drop is squeezed through the nozzle. Known vials often release drops larger than 30 microliters. As a result, medicament frequently drips onto the person's cheek and, depending upon the type of medicament, it may irritate the person's skin. Moreover, if the eye receives too large a drop or several drops, the eye may be subjected to an overdose of medicament. This condition can be extremely dangerous, especially if the patient is particularly sensitive to the medicament. For example, in some patients an overdose of beta blockers may cause severe side effects, such as bronchospasma or lowering of the heart rate, and may possibly cause death.
Another problem with known devices employing a squeeze vial or an eyedropper is that the medicament within the vial can easily become contaminated. Frequently people accidentally touch the conjunctiva of the eye with the tip of the vial or eyedropper. If the conjunctiva is infected, the tip of the nozzle can pick up the germs and contaminate the medicament that is squeezed into the tip. After the squeezing force is released from the device, the suction frequently draws medicament back into the device that was contaminated by contact with the tip. This problem is especially critical with devices employing ocumeters. The long and narrow tip of an ocumeter is more likely to accidentally touch the conjunctiva. Also, an ocumeter has a large volume of space, often referred to as "dead space," that holds medicament that is squeezed into the tip, but is not released into the eye. The medicament within the dead space, therefore, contacts the contaminated tip and, in turn, can contaminate the remainder of the medicament within the vial. This problem is exacerbated when the preservatives within the medicament, or the medicament itself, cannot destroy the particular germs or prevent repetitive contamination by the germs. Further use of the contaminated medicament may then only maintain or provoke a recurrence of the contaminating infection in the eye. This problem is especially critical shortly after eye surgery, for example, a corneal transplant, when the treated eye is most susceptible to infection.
Another problem with squeeze vials or eyedroppers is that the suction may force air bubbles into the drops of medicament. The air bubbles decrease the amount of medicament in each drop, and, accordingly, decrease the effectiveness of the treatment.
Yet another problem with known ocular treatment devices is that they are generally difficult to use with medicaments that must be mixed from two separate compounds or solutions shortly prior to use. For example, some medicaments require that two separate liquid solutions be mixed prior to use while, on the other hand, others require that a powder or other solid phase medicament be mixed with a liquid solvent prior to use. These medicaments usually cannot be premixed by the manufacturer because their shelf life after mixing is too short. When employing known devices, such medicaments are generally mixed by the user who is required to pour or stir one solution into the other, and then shake or stir the mixture to form a homogeneous solution. Frequently, elderly people have difficulty mixing the solutions because their hands may shake. As a result, they often spill part of one solution and do not obtain a proper mixture of medicament. Likewise, this procedure is confusing to many people because the user is required to first measure and then mix two separate solutions.
It is an object of the present invention, therefore, to provide an ocular treatment apparatus that overcomes the problems and disadvantages of known devices, and to provide an improved apparatus for applying medicament into an eye.